Gelatinizing wood



Patented June 7, 1927.

1 1,631,834 UNITED STATES PATENT OFFICE.

ABLIE WILLIAM SOHORGER, OF MADISON, WISCONSIN, ASSIGNOR, BY MESNE AS SIGNMENTS, TO WOOD CONVERSION COMB-ANY, OF OLOQUET, MINNESOTA, A COB PORATION OF DELAWARE.

No Drawing.

It has long been known that when chemical wood pulps (cellulose) are beaten-in the presence of water for an extended period, the fibrous structure is partially or totally destroyed and the pulp acquires a gelatinous consistenc This gelatinous cellulose, on drying, S1IlIlkS greatly, and in the form of sheets-warps badly if left to dry spontaneously; the dry sheet has a hard, horny consistency and in thin sheets is translucent. It is further characterized by a greater hygroscopicity than normal cellulose, and on boiling with dilute acids at atmospheric pressure, a greater reducing power towards Fehlings solution is obtained than from the same cellulose not gelatinized. The changes that cellulose undergoes in becoming gelatinized or hydrated are not fully understood. Intramolecular distension, hydrolysis and oxidation appear to take place with the formation of hydrocellulose, oxycellulose and so-called dextrines.

It is known that wood cellulose obtained from wood by removing the lignin or encrusting materials in whole or in part bychemical treatment, gelatinizes readily in the ordinary paper-makers beater, while mechanical pulp consisting of raw lignocellulose is but slightly aflected. It is also known that by treating substantially ure cellulose obtained from wood with aci s or alkalis the gelatinization of the cellulose may be secured -more rapidly (on beating with water) than without the treatment with the chemicals mentioned.

The fact that lignocellulose or wood is very difficult to hydrate is reco nized in the literature. Gross and Bevan Paper Making, 1911, p. 369) state that The hydration qualities of mechanical 'pulip are not very 'reat Sindall n Elementary anual of Paper Technology, 1906, 52) in discussing the hydration of pulps by heating, states: Mechanical wood pulp suffers little alteration by beating, and no good purpose is attained by any prolonged treatment.

I have found that if wood (lignocellulose) is treated with a small amount of alkali or ound in the presence of a small amount of alkali until it loses its fibrous structure, the lignocellulose can be easily gelatinized to a high degree. The gelatinization can be obtained by use of usual mechanical disinte- GELATINIZING woon.

Application filed Bay is, 1 21. Serial in. 470,933.

grating machines such as a ball mill, beater, or refiner, but for this mechanical disintegration I prefer grinding under ressure in a disk grinder. In the latter, t e cutting, shearing and pressing, very greatly promote hydration.

I am aware that previously, wood has been ground or beaten in the presence of alkali, butit has always been for the purpose of isolating the wood fibers as such, to fit them" for use in the manufacture of paper; while I, on the contrary, desire to destroy the fibrous structure and produce from them a structureless gelatinous mass not fit for paper manufacture, but useful in other Ways.

I am aware that it is possible to partially gelatinize wood by severe grinding with Water alone. But I have found that when the wood is ground in the presence of a dilute alkaline solution, gelatinization is much more complete and can be obtained in a decidedly shorter time, and with much less expenditure of energy.

The effect of grinding the wood of angiosperms is much more pronounced than in the case of most of the gymnosperms. If water-logged aspen, for example, is passed through adisk grinder six times, it shows but slight gelatinization. However, if finely shredded aspen is water-logged in a dilute solution of caustic soda, and passed with fresh water through the grinder six times, it shows a high degree of gelatinization. With sufficient grinding, followed by screening and drying, a hard, horn-like, translucent product ultimately can be obtained which resembles the product obtainable from sulphite pulp.

In the case of coniferous woods such as spruce, appreciable gelatinization is obtain-' ed in six grindings, but by treatment with alkali the same degree of elatinization can be attained in three grindings. ,In the case of western cedar, re eated grinding causes little gelatinization, ut by the use of caustic soda, gelatinization is readily obtained.

The alkali causes a swelling of the hemicellulose and cellulose, and dissolves some of the resins and incrusting materials that .be largely due to the action of the alkali cheapness.

on the hemicellulose present in the wood, resulting in hydration and hydrolysls.

I have found that all alkalis assist in hy-' dration but I prefer to use caustic soda ow ing to the rapidity of its action and lts I do not limit myself to caustic soda, however. I have found that any of the following procedures give good results:

1. The fine wood particles are allowed to stand in a dilute caustic soda solution until water-logged. The caustic solution is then removed by centrifuging or filtering, and water is added-to bring the mass to a proper consistency for grinding. It is then passed through the grinder three to six times.

2. The wood is treated with dilute caustlc soda solution and warmed up to 100 C., cooled, the alkaline solution removed, and the residue is ground with water.

3. The wood is ground directly with a dilute solution of caustic soda, either cold or hot. v

4. The wood is ground first in water alone and then gelatinization is completed by grindin in an alkali medium.

The a ove methods show that a wide range of treatment may be used, and since the wood can be merely soaked in the dilute alkali and subsequently ground in water to a gelatinous mass, it shows that the presence of even a very small amount of absorbed alkali has a remarkable effect in promoting gelatinization. I have used solutions containing from a trace up to 10% of caustic soda for treating the wood by any of the above procedures. Good results have been obtained with as little as A;% of caustic soda and I prefer caustic soda solutions having to 1% of caustic soda, either for soaking the wood preparatory to grinding, or for the solution in which the wood is ground.

A good method of procedure is the following: The wood ground or shredded to pass a 10 mesh sieve is treated in the cold with 6 .to 9 parts of a V per cent caustic soda solution, based .on the dryiweight of the wood employed, and passed through the grinder until the proper degree of gelatinization 1s secured. From .three to six grindings are useful articles of manufacture.

caustic soda remaining may be neutralized and utilized by adding an acid resin soap, that is, a resin soap containing free resin in colloidal solution. Alum or aluminum sulphate is then added in the usual way well known to those skilled in the art of sizing paper and similar products.

I have also found that the gelatinized- .amount of size necessary to waterproof the product. The addition of an excess of aluminum sulphate has a further beneficial cffect in that it renders the colloidal gelatinized wood irreversible on drying and reduces its hygroscopic power. Accordingly, when a resin size is not employed, I treat the alkaline gelatinized wood with an excess of aluminum sulphate, that is, more than is re quired to neutralize the alkali present.

By means of my process of gelatinization, I can obtain from sawdust,'or other wood waste, a dense, horn-like product having a sp. gr. of 1.35 to 1.55 that serves for many In makin this product, I proceed as follows: the wood, gelatinized in the manner described, is screened to remove any particles of wood that are not sufficiently gelatinized. It is then neutralized with acid oraluminum sulphate and heated to dissolve some of the impurities present. After centrifugin or filtering, a plastic mass is obtained t at can be molded into any desired shape, and then dried by any .suitable'means. Where the color is not of importance, it is not necessary to neutralize the alkali.

The product can be worked with tools like wood, and, in general, can be used in much the same way that wood is used. rleretofore, a somewhat similar material known as cellulith has been made from wood cellulose or half stuff, but this is much more expensive raw material than the lignocellulose or wood Waste used by me.

The gelatinized wood previous to drying can be made fireproof or waterproof by the methods ordinarily employed. It can also be colored by mixing the suitable pigments or by the use of dyes, for which it has a greater afiinity than ordinary wood.

"I have further found that gelatinized wood made by my method has great binding power and when mixed with fiber aggregates of any kind can be made into boards. For example, when 40 to 50% of gelatinized wood is uniformly mixed with 60 to 50%.by weight of fiber aggregates, such as may be obtained by shredding wood, and the whole pressed into a sheet, and dried, a dense,

may also be mixed with the gelatinized wood In some cases 1t 1s to make useful articles. of advantage to mix the gelatinized wood with fillers such as magnesia, clay, infusorlal earth and similar products.

As a departure from the preferred procedure above described, I may" proceed by grinding or otherwise mechanically d1s 1ntegrating the wood, either in an alkaline solution, as above described, and stopping the mechanical disintegration before the.

mass is entirely structureless. There is thus obtained a mixture of completely gelatinized and structureless wood mixed with wood fibres and aggregates that have gelatinized surface coatings. For the manufacture of wall board and similar products, this is a very useful material, for without addition of a filler, either of fibrous character or otherwise, the mass can be shaped while wet into the form of a board which, after pressing and drying is comparableto one made from a mixture of completely gelatinized and structureless wood with fibers and fiber aggregates added as described above. Or, if desired, the mechanical'disintegration and resultant gelatinization can be carried still further and the deficiency in fibrous material can be made up by additions of ungelatinized wood fiber or fiber aggregates supplemented, if desired, with magnesia, clay, infusorial earth and s1m1lar products, the same as if the partially gelatinized mass had been completely gelatinized. Preferably the mixture comprises 40 to 50% gelatinized wood.

By thus modifying the procedure to em-' body incomplete gelatinization of the wood,

' whether new and ungelatinized fibers or fiber aggregates be added or not, I obtain a product consisting of a mixture of fine structureless lignocellulose with fiber aggre gates uniformly distributed through it. Neither the fine structureless material, nor the coarse aggregates, nor the mixture of the two, is suitable for the manufacture of paper, and consequently, neither the product nor the process is comparable ,to disclosuresin the art of paper making, wherein woody materials have been beaten in an alkaline solution to separate the fibers and render them suitable for use in the manufacture of paper, even though as incidental to that beating there may have been a superficial gelatinization of the fibers.

In all the prior art patents, so far examined by me, where wood has been ground with alkali, the object has been to obtain fibers for the purpose of making paper. Nowhere have I found a disclosure of the grinding with alkali to convert the fibers 1nto a substantially structureless gelatinous mass to obtain benefit from the'gelatinizathe method and of the product without desolution or after treatment withan alkalme p arting from the spirit of my invention, as defined by theappended claims.

I claim 1 l. The method .of reducing wood to a gelatinous mass, which consists in mechanically disintegrating wood fibers that have been subjected to a small amount of alkali, substantially as described.

2. The method of reducing wood to a gelatinous mass, which consists in grinding the wood fibers in the presence of a small amount of alkali.

3. The method of reducing wood to a gelatinous mass, which consists in mechanically disintegrating the wood fibers in a dilute aqueous alkaline solution.

4. The method which consists in mechanically reducing 'wood in the presence of a small amount of alkali to a mixture made up partially of a structureless gelatinous mass, and partially of wood fibers and aggregates having gelatinized surfaces, substantially as described. 7

5. The method which consists in grinding wood under pressure in adisk grinder, in the presence of a dilute aqueous alkaline solution, until a gelatinous and substantially structureless mass is produced.

' 6. The method which consists in grinding wood in the presence of a dilute aqueous alkaline solution to a gelatinous mass and mixing the same with a fibrous filler.

7. The method which consists in grinding wood in the presence of a dilute aqueous alkaline solution to a gelatinous mass, waterproofing and fireproofing the same and mixing with a fibrous filler; substantially as described.

8. The method of reducing wood to a gelatinous mass, which consists in mechanically disintegrating woodfibers, said fibers having had treatment with a dilute aqueous solution of alkali at an elevated temperature but below the boiling point of water.

9. The method of reducing wood to a gelatinous, structureless mass, which consists in grinding the fibers in a dilute alkaline solution at an elevated temperature but below the boiling point of water.

10. The method which consists in mechanically disintegrating wood in the presence inous, structureless mass is Obtained, and drying such mass to a dense, horn-like body, substantially as described.

11. The method which consists in grinding Wood in the presence of a dilute caustic soda solution until a gelatinous, structureless mass is obtained and then neutralizing the caustic soda, filtering and drying to a dense, horn-like body.

12. The method which consists in grinding wood in the presence of a dilute caustic soda solution until a gelatinous, structure less mass is obtained, and then neutralizing the .caustic soda with an acid resin soap, filtering and drying to a dense, horn-like body.

In testimony whereof I affix my signature.

ARLIE WILLIAM S-CHORGER. 

